1. Field of the Invention
The present invention relates to building materials, and particularly to a thermal control insert for hollow blocks and a thermal resistant hollow block.
2. Description of the Related Art
Certain regions of the world experience high temperatures that can exceed comfort levels for habitability. Countries such as Saudi Arabia and other Arabian Gulf states can experience high ambient temperatures throughout the year. In these countries it can often be necessary for extensive use of air conditioning systems to maintain thermal comfort in buildings. For example, in Saudi Arabia, it is estimated that at least about 70% of the energy available for buildings is consumed by air conditioning alone. The rate of external heat penetrating into buildings, which is the main component of thermal load, can depend on a number of factors, such as the thermal resistance of the building materials.
External heat from an outside environment can penetrate into interiors of buildings in a number of ways. The external heat can penetrate by thermal processes such as conduction through solid joints in the building frame and by convection in the air filled cavities of hollow blocks, such as hollow bricks and cement blocks. The thermal performance and resistance of hollow blocks can depend on a number of factors, such as the number of cavities and the arrangement of the cavities in the hollow blocks, for example. Convection can allow for external heat to enter into the interior of the building because particles of fluid, such as air, located in the cavities can begin to move freely when heated, which can increase the kinetic energy of the fluid. As kinetic energy increases, the thermal resistance of the brick can decrease, thereby typically increasing the amount of heat entering into the interior of the building. Thus, temperature control inside the interior of the building can become harder to maintain, which can result in greater consumption of energy, such as to cool the building.
Current approaches to increase the thermal resistance of hollow blocks include changing the number of cavities or modifying the arrangement of cavities within the hollow block. Another approach is filling in the cavities of the hollow block with a material, such as rubber or polystyrene foam. However, these approaches typically only increase the thermal resistance of the hollow block by about 20% to about 30%. Further, the second approach of filling in the cavities with a material generally does not take into consideration the air within the cavity, since the air within the cavity is usually completely displaced by the filled in material. This can be detrimental because air typically has a lower conductivity value than rubber or polystyrene foam. For example, air has a conductivity value of about one-tenth that of rubber. This means air relatively has a greater thermal resistance R-value and, therefore, can act as a better insulator from external heat. Thus, it would be beneficial for the air to remain inside the cavities to provide for increased thermal resistance.
Therefore, it is desirable for a thermal control insert to increase the thermal resistance of a hollow block and reduce the heat transfer by natural convection inside the cavities of the hollow block and for a thermal resistant block to utilize the air located within its cavities.
Thus, a thermal control insert for hollow blocks and a thermal resistant hollow block addressing the aforementioned problems is desired.